A power conversion device which converts alternating current power of a commercial alternating current power supply into direct current power with high efficiency is needed in order to charge a power accumulator. Generally, a conventional power conversion device includes: an AC/DC converter section by which a commercial alternating current power supply is controlled with high power factor to perform alternating current/direct current conversion; and a DC/DC converter section which is placed at a subsequent stage thereof and is insulated between the primary side and the secondary side by a transformer, to supply to a load or to charge a battery.
As an example of such a power conversion device, a power conversion device disclosed in Patent Document 1 includes: a smoothing capacitor which smoothes direct current output of an AC/DC converter section that controls the power factor of an input alternating current with high efficiency to convert alternating current voltage into direct current voltage; and a DC/DC converter section that converts voltage of the smoothing capacitor into a secondary side direct current voltage insulated by a transformer, to supply to a load such as a battery. A control device of the power conversion device adjusts an output voltage target value of the AC/DC converter section in response to direct current output from the DC/DC converter section to the load; and thus, the variation width of a duty ratio of a semiconductor switching element in the DC/DC converter section can be suppressed and reduction in power loss at the DC/DC converter section is achieved to improve power conversion efficiency.
Furthermore, a power conversion device disclosed in Patent Document 2 includes a power converter which is composed of a main converter and a sub converter to convert alternating current power into direct current power; a charging resistor is further connected between the sub converter and an alternating current power supply; and a power accumulator of the sub converter is charged via this charging resistor during initial charging. A phase voltage of an input alternating current voltage can be shared by the main converter and the sub converter, which are connected in series; and thus, a pulse with high voltage does not need to perform switching by a high frequency and suppression of harmonics and reduction in power loss and electromagnetic noise can be achieved. The power accumulator of the sub converter is initially charged via the charging resistor; and thus, an inrush current to be flown into the power accumulator is prevented and the power accumulator can be charged.
Besides, a power conversion device disclosed in Patent Document 3 includes a switching circuit which performs direct current-alternating current conversion or alternating current-direct current conversion mutually between a direct current power supply and a power system. Then, the power conversion device further includes: a connection switch that connects the direct current power supply to the switching circuit; an interconnection switch that connects the switching circuit to the power system; a direct current side capacitor that smoothes direct current power between the connection switch and the switching circuit; and a filter capacitor that makes alternating current power of a predetermined frequency band pass through between the switching circuit and the interconnection switch. Then, alternating current power supplied from the power system is rectified to generate direct current power at start-up; and charging is performed up to a predetermined voltage to the direct current side capacitor via a charging resistor and to the filter capacitor via the switching circuit. Subsequently, the switching circuit is made to stop to charge the direct current side capacitor up to a rectified voltage of the power system; and then, connection of the interconnection switch and the connection switch and the operation of the switching circuit are restarted. This separates the load from the power conversion device during initial charging, and the power conversion device is connected to the load after reaching a state where initial charging has been completed and the influence of a subsequent stage load can be eliminated; and thus, suppression of an inrush current generated during the process of start-up is suppressed.